Revert of Analytic AntiAlias for Convex Shapes

src/core/SkAnalyticEdge.cpp

-/*
- * Copyright 2006 The Android Open Source Project
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-
-#include "SkAnalyticEdge.h"
-#include "SkFDot6.h"
-#include "SkMathPriv.h"
-#include "SkAAAConstants.h"
-
-class QuickFDot6Inverse {
-private:
-    static constexpr const SkFDot6* table = gFDot6INVERSE + kInverseTableSize;
-public:
-    inline static SkFixed Lookup(SkFDot6 x) {
-        SkASSERT(SkAbs32(x) < kInverseTableSize);
-        return table[x];
-    }
-};
-
-static inline SkFixed quickSkFDot6Div(SkFDot6 a, SkFDot6 b) {
-    if (SkAbs32(b) < kInverseTableSize) {
-        SkASSERT((int64_t)a * QuickFDot6Inverse::Lookup(b) <= SK_MaxS32);
-        SkFixed ourAnswer = (a * QuickFDot6Inverse::Lookup(b)) >> 6;
-        #ifdef SK_DEBUG
-        SkFixed directAnswer = SkFDot6Div(a, b);
-        SkASSERT(
-            (directAnswer == 0 && ourAnswer == 0) ||
-            SkFixedDiv(SkAbs32(directAnswer - ourAnswer), SkAbs32(directAnswer)) <= 1 << 10
-        );
-        #endif
-        return ourAnswer;
-    } else {
-        return SkFDot6Div(a, b);
-    }
-}
-
-// This will become a bottleneck for small ovals rendering if we call SkFixedDiv twice here.
-// Therefore, we'll let the outter function compute the slope once and send in the value.
-// Moreover, we'll compute fDY by quickly lookup the inverse table (if possible).
-bool SkAnalyticEdge::updateLine(SkFixed x0, SkFixed y0, SkFixed x1, SkFixed y1, SkFixed slope) {
-    // Since we send in the slope, we can no longer snap y inside this function.
-    // If we don't send in the slope, or we do some more sophisticated snapping, this function
-    // could be a performance bottleneck.
-    SkASSERT(fWinding == 1 || fWinding == -1);
-    SkASSERT(fCurveCount != 0);
-
-    SkASSERT(y0 <= y1);
-
-    SkFDot6 dx = SkFixedToFDot6(x1 - x0);
-    SkFDot6 dy = SkFixedToFDot6(y1 - y0);
-
-    // are we a zero-height line?
-    if (dy == 0) {
-        return false;
-    }
-
-    SkASSERT(slope < SK_MaxS32);
-
-    SkFDot6     absSlope = SkAbs32(SkFixedToFDot6(slope));
-    fX          = x0;
-    fDX         = slope;
-    fUpperX     = x0;
-    fY          = y0;
-    fUpperY     = y0;
-    fLowerY     = y1;
-    fDY         = (absSlope | dx) == 0
-                  ? SK_MaxS32
-                  : absSlope < kInverseTableSize
-                    ? QuickFDot6Inverse::Lookup(absSlope)
-                    : SkAbs32(quickSkFDot6Div(dy, dx));
-
-    return true;
-}
-
-void SkAnalyticEdge::chopLineWithClip(const SkIRect& clip) {
-    int top = SkFixedFloorToInt(fUpperY);
-
-    SkASSERT(top < clip.fBottom);
-
-    // clip the line to the clip top
-    if (top < clip.fTop) {
-        SkASSERT(SkFixedCeilToInt(fLowerY) > clip.fTop);
-        SkFixed newY = SkIntToFixed(clip.fTop);
-        this->goY(newY);
-        fUpperY = newY;
-    }
-}
-
-bool SkAnalyticQuadraticEdge::setQuadratic(const SkPoint pts[3]) {
-    if (!fQEdge.setQuadraticWithoutUpdate(pts, 2)) {
-        return false;
-    }
-    fQEdge.fQx >>= 2;
-    fQEdge.fQy >>= 2;
-    fQEdge.fQDx >>= 2;
-    fQEdge.fQDy >>= 2;
-    fQEdge.fQDDx >>= 2;
-    fQEdge.fQDDy >>= 2;
-    fQEdge.fQLastX >>= 2;
-    fQEdge.fQLastY >>= 2;
-    fQEdge.fQy = snapY(fQEdge.fQy);
-    fQEdge.fQLastY = snapY(fQEdge.fQLastY);
-
-    fWinding = fQEdge.fWinding;
-    fCurveCount = fQEdge.fCurveCount;
-    fCurveShift = fQEdge.fCurveShift;
-
-    fSnappedX = fQEdge.fQx;
-    fSnappedY = fQEdge.fQy;
-
-    return this->updateQuadratic();
-}
-
-bool SkAnalyticQuadraticEdge::updateQuadratic() {
-    int     success = 0; // initialize to fail!
-    int     count = fCurveCount;
-    SkFixed oldx = fQEdge.fQx;
-    SkFixed oldy = fQEdge.fQy;
-    SkFixed dx = fQEdge.fQDx;
-    SkFixed dy = fQEdge.fQDy;
-    SkFixed newx, newy, newSnappedX, newSnappedY;
-    int     shift = fCurveShift;
-
-    SkASSERT(count > 0);
-
-    do {
-        SkFixed slope;
-        if (--count > 0)
-        {
-            newx    = oldx + (dx >> shift);
-            newy    = snapY(oldy + (dy >> shift));
-            slope = dy >> 10 > 0 ? quickSkFDot6Div(dx >> 10, dy >> 10) : SK_MaxS32;
-            if (SkAbs32(dy) >= SK_Fixed1 * 2) { // only snap when dy is large enough
-                newSnappedY = SkTMin<SkFixed>(fQEdge.fQLastY, SkFixedRoundToFixed(newy));
-                newSnappedX = newx + SkFixedMul_lowprec(slope, newSnappedY - newy);
-            } else {
-                newSnappedY = newy;
-                newSnappedX = newx;
-            }
-            dx += fQEdge.fQDDx;
-            dy += fQEdge.fQDDy;
-        }
-        else    // last segment
-        {
-            newx    = fQEdge.fQLastX;
-            newy    = fQEdge.fQLastY;
-            newSnappedY = newy;
-            newSnappedX = newx;
-            slope = (newSnappedY - fSnappedY) >> 10
-                    ? quickSkFDot6Div((newx - fSnappedX) >> 10, (newy - fSnappedY) >> 10)
-                    : SK_MaxS32;
-        }
-        if (slope < SK_MaxS32) {
-            success = this->updateLine(fSnappedX, fSnappedY, newSnappedX, newSnappedY, slope);
-        }
-        oldx = newx;
-        oldy = newy;
-    } while (count > 0 && !success);
-
-    SkASSERT(newSnappedY <= fQEdge.fQLastY);
-
-    fQEdge.fQx  = newx;
-    fQEdge.fQy  = newy;
-    fQEdge.fQDx = dx;
-    fQEdge.fQDy = dy;
-    fSnappedX   = newSnappedX;
-    fSnappedY   = newSnappedY;
-    fCurveCount = SkToS8(count);
-    return success;
-}
-
-bool SkAnalyticCubicEdge::setCubic(const SkPoint pts[4]) {
-    if (!fCEdge.setCubicWithoutUpdate(pts, 2)) {
-        return false;
-    }
-
-    fCEdge.fCx >>= 2;
-    fCEdge.fCy >>= 2;
-    fCEdge.fCDx >>= 2;
-    fCEdge.fCDy >>= 2;
-    fCEdge.fCDDx >>= 2;
-    fCEdge.fCDDy >>= 2;
-    fCEdge.fCDDDx >>= 2;
-    fCEdge.fCDDDy >>= 2;
-    fCEdge.fCLastX >>= 2;
-    fCEdge.fCLastY >>= 2;
-    fCEdge.fCy = snapY(fCEdge.fCy);
-    fCEdge.fCLastY = snapY(fCEdge.fCLastY);
-
-    fWinding = fCEdge.fWinding;
-    fCurveCount = fCEdge.fCurveCount;
-    fCurveShift = fCEdge.fCurveShift;
-    fCubicDShift = fCEdge.fCubicDShift;
-
-    return this->updateCubic();
-}
-
-bool SkAnalyticCubicEdge::updateCubic() {
-    int     success;
-    int     count = fCurveCount;
-    SkFixed oldx = fCEdge.fCx;
-    SkFixed oldy = fCEdge.fCy;
-    SkFixed newx, newy;
-    const int ddshift = fCurveShift;
-    const int dshift = fCubicDShift;
-
-    SkASSERT(count < 0);
-
-    do {
-        if (++count < 0) {
-            newx    = oldx + (fCEdge.fCDx >> dshift);
-            fCEdge.fCDx    += fCEdge.fCDDx >> ddshift;
-            fCEdge.fCDDx   += fCEdge.fCDDDx;
-
-            newy    = oldy + (fCEdge.fCDy >> dshift);
-            fCEdge.fCDy    += fCEdge.fCDDy >> ddshift;
-            fCEdge.fCDDy   += fCEdge.fCDDDy;
-        }
-        else {    // last segment
-            newx    = fCEdge.fCLastX;
-            newy    = fCEdge.fCLastY;
-        }
-
-        // we want to say SkASSERT(oldy <= newy), but our finite fixedpoint
-        // doesn't always achieve that, so we have to explicitly pin it here.
-        if (newy < oldy) {
-            newy = oldy;
-        }
-
-        success = this->updateLine(oldx, oldy, newx, newy,
-                SkFixedToFDot6(newy - oldy) == 0 ? SK_MaxS32 :
-                        SkFDot6Div(SkFixedToFDot6(newx - oldx), SkFixedToFDot6(newy - oldy)));
-        oldx = newx;
-        oldy = newy;
-    } while (count < 0 && !success);
-
-    fCEdge.fCx  = newx;
-    fCEdge.fCy  = newy;
-    fCurveCount = SkToS8(count);
-    return success;
-}